For STEM kids who love to build: This marble rails booster set contains 325 pieces total. Including glass marbles and 30+ rail action pieces Marbles included: This set includes 45 standard-sized glass marbles. Kiddos will love watching them fly through the plastic rails and tubes Designed for kids: All Marble Genius sets are challenging enough for adults and yet easy for kids to use. Our kid-friendly connectors fit together snugly and provide a stable structure Free app with purchase: Download the Marble Genius instruction application for step-by-step guidance, fun challenges, and regularly updated content. iOS and Android versions Endless options: All Marble Genius products are compatible. Our marble run sets, marble maze games, and accessory sets can all be used together Marble Genius offers creative STEM learning for everyone, with a dose of action, thrills and excitement thrown in for good measure. Dig in to the engineering challenge of designing and building a marble run, then sit back and watch the action unfold. See-through structural pieces let you watch marbles in motion. Our free app gives you the option to share races with your friends online. And our new rails playsets offer a whole new kind of rolling marble action. Let the building fun begin!